ramips: fix GB-PC1/PC2 build error

With ed25e3ac02 ("ramips: fix some clocks in mt7621.dtsi") the
cpuclock node was dropped from the mt7621.dtsi without removing the
references to this node from the GB-PC1/PC2 dts files.

Remove them now, to fix the build error.

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/ramips/dts/GB-PC1.dts

@@ -105,11 +105,6 @@
 	};
 };
 
-&cpuclock {
-	compatible = "fixed-clock";
-	clock-frequency = <900000000>;
-};
-
 &pcie {
 	status = "okay";
 };

target/linux/ramips/dts/GB-PC2.dts

@@ -115,11 +115,6 @@
 	};
 };
 
-&cpuclock {
-	compatible = "fixed-clock";
-	clock-frequency = <900000000>;
-};
-
 &pcie {
 	status = "okay";
 };